Jupiter

The largest planet in the solar system, Jupiter is the fifth planet in order from the Sun and marks the beginning of the outer solar system. It is a gas giant planet with a diameter eleven times that of the Earth. Although the most massive of the planets, it is still dwarfed by the Sun, containing only 0.1 per cent of a solar mass. Its composition is the same as that of the Sun's, however, being mostly hydrogen and helium with only traces of the other elements. Jupiter, in common with the other gas giants has no solid surface. Instead, its atmosphere becomes thicker and thicker until the hydrogen is compressed into exotic states of matter which behave more like a metal than a gas. The cloud tops contain belts and zones of colour thought to indicate the depth and composition of the clouds. Also visible are huge cyclonic storms such as the great red spot. Jupiter possesses sixteen natural satellites, four of which are easily visible to observers on the Earth. They are known as the Galilean satellites and, in order of distance from Jupiter, are Io, Europa, Ganymede and Callisto. Its equatorial radius is 71,500 km and its mass 1.9 x 10²⁸ kg.